In: Chemistry
For each of the following processes, use a calculation to
predict whether or not it will
occur spontaneously. (For some cases you may need to use data from
Appendix A in
your textbook.)
a) A piston with radius of 15.6 cm containing 2.86 L of an ideal
gas (Cv,m = 3/2 R) at
1.00 atm, 298.15 K undergoes isothermal compression by the addition
of a 5.64
kg weight.
b) The combustion reaction for methanol CH4O(l) at 298.15 K carried
out in a bomb
calorimeter.
c) Evaporation of 10.00oC liquid water under standard conditions,
given that ΔHo
vap
= 44.120 kJ/mol at 298.15 K. Temperature-independent heat capacity
for water:
Cp,m(H2O(l)) =75.327 kJ mol-1; Cp,m(H2O(g))=33.651 kJ mol-1
First let´s calculate the the area of the piston
15.6 cm = 0.156 m = radius
A = = 3.1416 * 0.156 * 0.156 = 0.0764 m2
Let´s calculate the force the mass has = 5.64 * 9.81 = 55.32 N , this is by multiplying the kg by the gravity
now remember how to relate force with pressure
Pressure = Force / Area
Pressure = 55.32 / 0.0764 = 724.08 Pascal
Let´s change this value to atm, 724.08 Pa = 0.00714611399 atm
Final pressure = 1 + 0.00715 = 1.007 atm
moles of gas
PV = nRT, p is pressure, V is volume, R is gas constant and T is temperature
1 atm * 2.86 = n * 0.082*298.15
n = 1*2.86/(0.082*298.15) = 0.11698 moles of gas
for volume 2 we use the relationship
P1V1 = P2V2
1 atm * 2.86 = 1.007 * V2
V2 = 2.86 / 1.007 = 2.84 L,
let´s apply formula
S change = 0.1167*0.082 * ln(2.84/2.86) = -0.00006715
According to calculations this is a non spontaneous process
*Just 1 question at a time please =)